Toxicology: Pharmacy - Principles of toxicology

Question 1

Formula for anion gap. What is normal?

Answer 1

(Na+ + K+) - (Cl- + HCO3-)
Normal is 12-16 (or 8-12 if K+ omitted)

Question 2

10 drug-related causes of HAGMA. Which of these cause lactic acidosis?

Answer 2

Organic acid metabolites:
1. Methanol
2. Ethylene glycol / diethylene glycol
3. Oxoprolinuria (rare complication of paracetamol)

Lactic acidosis:
4. Cyanide
5. CO
6. Ibuprofen
7. Isoniazide
8. Metformin
9. Salicylates
10. Valproate

Question 3

Five drugs which cause hyperkalaemia

Answer 3

1. Exogenous K+
2. K+-sparing diuretics
3. B-blockers
4. Digoxin
5. Fluoride

Question 4

Four drugs which cause hypokalaemia

Answer 4

1. Barium
2. Thiazide and loop diuretics
3. B-agonists
4. Caffeine, theophylline

Question 5

Formula for serum osmolality. What is normal?

Answer 5

Osmolality = 2 x Na+ + (glucose/18) + (BUN/3)
Normally 280-290 mOsm/L

Question 6

How is osmolar gap calculated?

Answer 6

Omsolar gap = measured - calculated

Question 7

Six drugs which produce an increased osmolar gap

Answer 7

1. Acetone
2. Ethanol
3. Ethylene glycol
4. Isopropyl alcohol
5. Methanol
6. Propylene glycol

Question 8

Two classes of drugs which cause QRS widening

Answer 8

1. TCAs
2. Na+ channel blockade

Question 9

Three classes of drugs which cause QTc prolongation

Answer 9

1. Antidepressants/antipsychotics
2. Lithium
3. Arsenic

Question 10

Three methods of gastric decontamination

Answer 10

1. Gastric lavage
2. Activated charcoal
3. Laxatives

Question 11

Three drugs which are not bound by activated charcoal, and two which bind poorly

Answer 11

Do not bind:
1. Lithium
2. Iron
3. Potassium

Poorly bound:
1. Alcohol
2. Cyanide

Question 12

At what ratio should activated charcoal be administered?

Answer 12

10:1 charcoal:toxin

Question 13

Four poisonings for which laxatives can be used for GI decontamination

Answer 13

1. Iron tablets
2. Enteric-coated medicines
3. Drug-filled packets
4. Foreign bodies

Question 14

Nine drugs for which haemodialysis is useful

Answer 14

1. Carbamazepine
2. Ethylene glycol
3. Lithium
4. Methanol
5. Metformin
6. Phenobarbital
7. Salicylate
8. Theophylline
9. Valproate

Question 15

Eight drugs for which haemodialysis is not useful

Answer 15

1. Amphetamines
2. Antidepressants
3. Antipsychotics
4. Benzodiazepines
5. CCBs
6. Digoxin
7. Metoprolol, propranolol
8. Opioids

Question 16

Two drugs for which urinary alkalinisation is useful

Answer 16

1. Salicylates
2. Phenobarbital

Question 17

Two drugs for which urinary acidification is useful. Why is this not practiced clinically?

Answer 17

Increased clearance of PCP and amphetamines
Not practiced clinically as increases risk of renal complications due to rhabdomyolysis

Question 18

Antidote for anticholinesterase poisoning

Answer 18

Atropine

Question 19

Antidote for organophosphate poisoning

Answer 19

Atropine

Question 20

Antidote for membrane-depressant cardiotoxic drugs (e.g. TCAs, quinidine)

Answer 20

Sodium bicarbonate

Question 21

Antidote for fluoride poisoning

Answer 21

Calcium

Question 22

Antidote for CCBs poisoning

Answer 22

Calcium

Question 23

Antidote for iron salts poisoning

Answer 23

Deferoxamine

Question 24

Antidote for digoxin poisoning

Answer 24

Digoxin Ab (Digibind)

Question 25

Antidote for theophylline and caffeine poisoning

Answer 25

Esmolol

Question 26

Antidote for methanol and ethylene glycol poisoning

Answer 26

Ethanol
Fomepizole

Question 27

Antidote for benzodiazepine poisoning

Answer 27

Flumazenil

Question 28

Antidote for B-blockers poisoning

Answer 28

Glucagon

Question 29

Antidote for cyanide poisoning

Answer 29

Hydroxocobalamin

Question 30

Antidote for narcotic poisoning

Answer 30

Naloxone

Question 31

Antidote for CO poisoning

Answer 31

Oxygen

Question 32

Antidote for anticholinergic delirium

Answer 32

Physostigmine

Question 33

Antidote for organophosphate cholinesterase inhibitors

Answer 33

Pralidoxime (2-PAM)

Question 34

When should NAC be given for best results?

Answer 34

Within 8-10hrs of paracetamol overdose

Question 35

What are the therapeutic endpoints used in treating anticholinesterase and organophosphate poisoning?

Answer 35

Wheezing
Pulmonary secretions

Question 36

What dose of sodium bicarbonate is used for membrane-depressant cardiotoxic drug poisoning?

Answer 36

1-2mg/kg

Question 37

Two indications for Digibind

Answer 37

Serious arrhythmias
Hyperkalaemia

Question 38

What blood ethanol level should be aimed for when treating ethylene glycol or methanol poisoning?

Answer 38

100mg/dL (loading dose needed)

Question 39

What dose of flumazenil should be given in benzodiazepine overdose?

Answer 39

0.2mg repeated as needed to maximum 3g

Question 40

Three contraindications for flumazenil in benzodiazepine overdose

Answer 40

1. Seizures
2. Benzodiazepine overdose
3. TCA overdose

Question 41

Dose of fomepizole for ethylene glycol or methanol poisoning

Answer 41

15mg/kg every 12hrs

Question 42

Dose of glucagon used to treat B-blocker overdose

Answer 42

5-10mg may reverse hypotension and bradycardia

Question 43

What is the mechanism of action of hydroxocobalamin in cyanide poisoning?

Answer 43

Converts cyanide to cyanocobalamin (vitamin B12)

Question 44

How is naloxone dosed in narcotic overdose?

Answer 44

0.4-2mg initially (may need to be repeated as duration of action of 2-3hrs may be shorter than that of the opioid)

Question 45

Three narcotics for which an increased dose of naloxone may be needed

Answer 45

1. Propoxyphene
2. Codeine
3. Fentanyl

Question 46

Three adverse effects of physostigmine

Answer 46

1. Bradycardia
2. Increased bronchial secretions
3. Seizure